Is it OK to get dermal fillers a few days after minor surgery?

It should be okay to proceed with injectables after the procedures you are describing.  Each procedure and anesthesia is different, so make sure that the injector knows exactly what you are going to do.  Remember that patients should be off of things that can cause the blood to be, "thin", and cause bleeding or brusing. (i.e. aspirin, ibuprofen, ginko, etc;).
It is important to communicate with your experienced injector and be on the "same page" as to the desired result.  Please have reasonable expectations.   
Jeffrey J. Roth, M.D., F.A.C.S.
Board Certified Plastic Surgeon
Las Vegas Plastic Surgery

In my opinion, it would be fine to have lip fillers done 3 days after a colonoscopy and endoscopy which involved anesthesia.  There should be no interaction between the two events.   

There is no reason you can't get injectable fillers after having a colonoscopy/endoscopy under anesthesia. As long as you're feeling well and not taking any blood thinners it will be fine. It would certainly be preferable to have it done after the procedure compared to before since the endoscopy will require some manipulation of your lips.